Katariina, an orphaned girl from the north, travels to Helsinki to live with her distant relative Mauri, who has been appointed her guardian. The unpretentious child of nature irritates, amuses, and charms Mauri, who is accustomed to high society, and his bachelor friends.

The strange, disjointed love story in the existentialist film Windy Day transported the young lovers to an island off the town of Kotka.